This invention relates to integrated circuits, and more particularly, to low-voltage programmable electrical fuses used in integrated circuits.
Integrated circuits sometimes contain nonvolatile memory elements. Nonvolatile memory is used for persistent data storage and need not be reprogrammable. Rather, one-time use scenarios are acceptable. Examples of situations in which one-time programmable nonvolatile memory elements such as one-time programmable fuses and antifuses may be used include situations in which a unique identification code is loaded onto an integrated circuit or in which repair settings are permanently loaded-into an integrated circuit as part of a manufacturing process. Repair settings might, for example, permanently switch redundant circuitry into use in place of defective circuitry, thereby effectuating a permanent repair of the integrated circuit before shipping to an end user.
When forming nonvolatile memory elements for applications such as redundancy schemes and permanent data storage, it is desirable to select a memory element technology that exhibits satisfactory levels of permanency and power consumption. Traditional nonvolatile memory elements are sometimes formed using laser-programmed links or electrically programmable fuses. Laser programming of nonvolatile memory elements requires special programming tools that can add undesirable cost and complexity to the manufacturing process. Electrically programmable fuses are often preferred over laser fuses as they have a significantly lower production cost than laser fuses and may be programmed once the integrated circuit containing the fuse is already packaged. In use, a predetermined programming voltage is required to program or blow such electrical fuses. Generally, it is desirable for the predetermined programming voltage to be compatible with the voltages required by the remainder of the integrated circuit. However, as the geometries of integrated circuits decrease with each technology node, the voltages required by the remainder of the integrated circuit have lowered significantly, and integrated circuits with electrically programmable fuses may require additional power sources and circuit routing for programming or blowing the electrically programmable fuses.
It would therefore be desirable to be able to provide improved electrically programmable fuse circuitry for integrated circuits that is capable of being persistently programmed or blown at low voltages.